Method Of Improving Ion Beam Quality In A Non-Mass-Analyzed Ion Implantation System

ABSTRACT

A method of processing a workpiece is disclosed, where the plasma chamber is first coated using a conditioning gas and optionally, a co-gas. The conditioning gas, which is disposed within a conditioning gas container may comprise a hydride of the desired dopant species and a filler gas, where the filler gas is a hydride of a Group 4 or Group 5 element. The remainder of the conditioning gas container may comprise hydrogen gas. Following this conditioning process, a feedgas, which comprises fluorine and the desired dopant species, is introduced to the plasma chamber and ionized. Ions are then extracted from the plasma chamber and accelerated toward the workpiece, where they are implanted without being first mass analyzed. In some embodiments, the desired dopant species may be boron.

This application is a continuation of U.S. patent application Ser. No.15/592,823 filed May 11, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/298,251 filed Jun. 6, 2014 (now U.S. Pat. No.9,677,171 issued Jun. 13, 2017), the disclosures of which areincorporated herein by reference in its entirety.

FIELD

Embodiments of the present disclosure relate to methods for improvingion beam quality in a non-mass-analyzed ion implantation system, andmore particularly, improving boron ion beam quality.

BACKGROUND

Semiconductor workpieces are often implanted with dopant species tocreate a desired conductivity. For example, solar cells may be implantedwith a dopant species to create an emitter region. This implant may bedone using a variety of different mechanisms. In one embodiment, an ionsource is used. This ion source may include a plasma chamber in whichsource gasses are ionized. The ions from these source gasses may beextracted through an aperture in the plasma chamber, using one or moreelectrodes. These extracted ions are directed toward a workpiece, wherethey are implanted in the workpiece to form the solar cell.

In an effort to improve process efficiency and lower cost, in someembodiments, the ions extracted from the ion source are accelerateddirectly toward the workpiece, without any mass analysis. In otherwords, the ions that are generated in the ion source are accelerated andimplanted directly into the workpiece. A mass analyzer is used to removeundesired species from the ion beam. Removal of the mass analyzerimplies that all ions extracted from the ion source will be implanted inthe workpiece. Consequently, undesired ions, which may also be generatedwithin the ion source, are then implanted in the workpiece.

This phenomenon may be most pronounced when the source gas is ahalogen-based compound, such as a fluoride. Fluorine ions and neutrals(metastable or excited) may react with the inner surfaces of the ionsource, releasing unwanted ions and neutrals, such as silicon, fluorine,oxygen, carbon, and aluminum and heavy metals present as impurityelements.

Therefore, a method that improves beam quality, particularly forembodiments in which halogen based boron-containing source gasses areemployed, would be beneficial.

SUMMARY

A method of processing a workpiece is disclosed, where the plasmachamber is first coated using a conditioning gas and optionally, aco-gas. The conditioning gas, which is disposed within a conditioninggas container, may comprise a hydride of the desired dopant species anda filler gas, where the filler gas is a hydride of a Group 4 or Group 5element. The remainder of the conditioning gas container may comprisehydrogen gas. Following this conditioning process, a feedgas, whichcomprises fluorine and the desired dopant species, is introduced to theplasma chamber and ionized. Ions are then extracted from the plasmachamber and accelerated toward the workpiece, where they are implantedwithout being first mass analyzed. In some embodiments, the desireddopant species may be boron.

According to one embodiment, a method of processing a workpiece isdisclosed. The method comprises performing a conditioning process, theconditioning process comprising: introducing a conditioning gas into aplasma chamber of an ion source from a conditioning gas container, theconditioning gas disposed in the conditioning gas container comprising ahydride containing a desired dopant species and a filler gas, where thefiller gas comprises a hydride of a Group 4 element or a hydride of aspecies having an opposite conductivity of the desired dopant species;and ionizing the conditioning gas in the plasma chamber so as to form acoating on walls of the plasma chamber; and performing an ionimplantation process after the conditioning process, the ionimplantation process comprising: introducing a feedgas into the plasmachamber from a feedgas container after the coating is formed, thefeedgas comprising fluorine and the desired dopant species; ionizing thefeedgas in the plasma chamber to create ions; and extracting the ionsfrom the plasma chamber and accelerating the ions toward the workpiece,such that the ions are implanted into the workpiece without massanalysis.

According to another embodiment, a method of processing a workpiece isdisclosed. The method comprises performing a conditioning process, theconditioning process comprising: introducing a conditioning gas into aplasma chamber of an ion source from a conditioning gas container, theconditioning gas disposed in the conditioning gas container comprising aborane and a filler gas, where the filler gas comprises a hydride of aGroup 4 element or a hydride of a Group 5 element; and ionizing theconditioning gas in the plasma chamber so as to form a coating on wallsof the plasma chamber, wherein the coating comprises boron and the Group4 or 5 element; and performing an ion implantation process after theconditioning process, the ion implantation process comprising:introducing a feedgas into the plasma chamber from a feedgas containerafter the coating is formed, the feedgas comprising fluorine and boron;ionizing the feedgas in the plasma chamber to create ions; andextracting the ions from the plasma chamber and accelerating the ionstoward the workpiece.

According to another embodiment, a method of coating the walls of aplasma chamber in an ion source is disclosed. The method comprises:providing conditioning gas in a conditioning gas container, wherein theconditioning gas comprises diborane and a filler gas, the filler gascomprising a hydride of a Group 4 element or a hydride of a Group 5element; introducing the conditioning gas from the conditioning gascontainer into the plasma chamber; and ionizing the conditioning gas soas to form a plasma, wherein ions from the plasma coat the walls of theplasma chamber with boron and the Group 4 or 5 element.

BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the present disclosure, reference is madeto the accompanying drawings, which are incorporated herein by referenceand in which:

FIGS. 1A-1B show the implant system according to different embodiments;and

FIG. 2 is a representative graph showing ion mass spectrum during aconditioning process.

DETAILED DESCRIPTION

As described above, ionization of halogen-based species, such asfluorides, may cause particles released from the inner surfaces of theion source to be implanted in the workpiece. These contaminants mayinclude aluminum, carbon, nitrogen, oxygen, silicon, fluorine-basedcompounds, and other unwanted species (including heavy metals present asimpurity elements). One approach to address the damage caused by freehalogen ions may be to introduce at least one additional source gasduring implantation. Another approach may be to condition the plasmachamber walls of the ion source prior to the ion implantation process.

FIGS. 1A-1B show various embodiments in which a second source gas andoptionally a third source gas may be introduced to a plasma chamber 105of an ion source 100. In each of these figures, the ion source 100includes a plasma chamber 105 defined by several plasma chamber walls107, which may be constructed from graphite or another suitablematerial. This plasma chamber 105 may be supplied with one or morefeedgasses, stored in a feedgas container 170, via a gas inlet 110. Thisfeedgas may be energized by an RF antenna 120 or anotherplasma-generation mechanism. The RF antenna 120 is in electricalcommunication with a RF power supply (not shown) which supplies power tothe RF antenna 120. A dielectric window 125, such as a quartz or aluminawindow, may be disposed between the RF antenna 120 and the interior ofthe plasma chamber 105. The ion source 100 also includes an aperture 140through which ions may pass. A negative voltage is applied to extractionsuppression electrode 130 disposed outside the aperture 140 to extractand focus the positively charged ions from within the plasma chamber 105through the aperture 140 and toward the workpiece 160. A groundelectrode 150 may also be employed. In some embodiments, the aperture140 is located on the side of the ion source 100 opposite the sidecontaining the dielectric window 125. Ions extracted from the plasmachamber 105 are formed into an extracted ion beam 180, which is directedtoward the workpiece 160. As described above, no mass analyzer is usedto filter out the unwanted ions before they strike the workpiece 160. Inone particular embodiment, shown in FIG. 1A, the second source gas maybe stored in a conditioning gas container 175 and introduced to theplasma chamber 105 through a second gas inlet 111. The third source gasmay be stored in a third gas container 176 and introduced to the plasmachamber 105 through a third gas inlet 112. In another embodiment, shownin FIG. 1B, the second source gas may be stored in a conditioning gascontainer 175 and the third source gas may be stored in a third gascontainer 176. Both the second source gas and the third source gas maybe introduced to the plasma chamber 105 through the same gas inlet 110used by the first source gas.

In any of these embodiments, the first source gas, the second source gasand the third source gas may be introduced simultaneously orsequentially to the plasma chamber 105. It should be noted that in someembodiments, more or less than three source gasses may be used. Forexample, in some embodiments, the third source gas, disposed in thirdgas container 176, is not used.

FIGS. 1A-1B utilize an ion source having a RF antenna 120 and an RFpower supply to generate the necessary ions. However, it can beappreciated that other types of ion sources may be used including IHC,hollow-cathode, helicon, and microwave ion source. For example, anindirectly heated cathode (IHC) which uses heat to cause thermionicemission of electrons may also be used in some embodiments. Other ionsources are also within the scope of the disclosure.

The first source gas, also referred to as the feedgas, may comprise adopant, such as boron, in combination with a halogen, such as fluorine.Thus, the feed gas may be in the form of DF_(n) or D_(m)F_(n), where Drepresents the dopant atom, which may be boron, gallium, phosphorus,arsenic or another Group 3 or Group 5 element. This first source gas maybe disposed within feedgas container 170.

The second source gas, also referred to as the conditioning gas, may bedisposed in conditioning gas container 175 and comprises a mixtureincluding molecules having a chemical formula of DH_(n) or D_(m)H_(n),where H is hydrogen, and one or more filler gasses. D may be a dopantspecies, such as any of those described above. In embodiments where thedopant is boron, the conditioning gas may include a borane, where thefiller gas is typically hydrogen gas. Boranes, and specificallydiborane, are not stable and therefore are usually stored in gascontainers with a large amount of hydrogen gas to improve theirmolecular stability. Otherwise, diborane quickly decomposes to formsolid boron and hydrogen. In some embodiments, conditioning gascontainer 175 may contain between 15-30% diborane with the remainderbeing hydrogen gas.

In other words, the feedgas may be BF₃ or B₂F₄, while the conditioninggas may be, for example, a mixture of hydrogen gas and B₂H₆. It isunderstood that other feedgas species and conditioning species are alsopossible.

In other embodiments, the conditioning gas stored in conditioning gascontainer 175 may be diborane mixed with hydrogen gas and at least oneadditional filler gas, such as a hydride of a Group 4 or Group 5element, including but not limited to phosphine (PH₃), silane (SiH₄),disilane (Si₂H₆) and germane (GeH₄). In these embodiments, the mixturewithin the conditioning gas container 175 may be 15-30% diborane, 10-30%filler gas, with the remainder being hydrogen gas. In some embodiments,less than 60% of the conditioning gas is made up of hydrogen gas. Inother embodiments, less than 50% of the conditioning gas is made up ofhydrogen gas.

The third source gas, referred to as the co-gas, may be disposed inthird gas container 176. In some embodiments, the co-gas may be a noblegas, such as helium, argon, krypton or xenon. In other embodiments, theco-gas may be a hydride containing a Group 4 element, such as but notlimited to silicon (i.e. silane, SH₄ or disilane, Si₂H₆ or germanium(i.e. germane, GeH₄). In yet other embodiments, the co-gas may be ahydride containing a species of the opposite conductivity as the desireddopant. In other words, if the feedgas contains boron, a hydridecontaining a Group 5 element may be used as the co-gas. The co-gas, inthis scenario, may be phosphine (PH₃) or arsine (AsH₃). It is noted thatin some embodiments, the third source gas is not used. In someembodiments, the co-gas may be the same species as the filler gas.

This combination of three source gasses can be used in two differentmodes in the ion source 100. In a first mode, known as ion implantationmode, a plasma of the desired dopant is created in the ion source 100.Ions of the desired dopant are then extracted from the ion source 100and accelerated toward the workpiece 160. In a second mode, orconditioning mode, a plasma is created. However, the purpose of theconditioning mode is not to implant the workpiece 160. Rather,conditioning is a process where material is coated onto the innersurfaces of the plasma chamber walls 107. This material may serve toprotect the plasma chamber walls 107 from the deleterious effects ofhalogens, reducing the amount of contaminants that are etched from theplasma chamber walls 107 and introduced into the extracted ion beam 180.

Conditioning may be performed in a number of ways. In a firstembodiment, conditioning is performed in the same manner asimplantation. In other words, a plasma is generated within plasmachamber 105 using energy from the RF antenna 120 or other plasmagenerator. Ions from that plasma are then extracted from the plasmachamber 105 through application of bias voltages to the electrodes 130,150. During this time, ions and excited or metastable neutrals from theplasma that are not extracted may be deposited on the plasma chamberwalls 107 of the plasma chamber 105, as well as the dielectric window125.

In a second embodiment, the bias voltages are not applied to theelectrodes 130, 150. Alternatively, a positive voltage can be applied toelectrodes 130 to repel the ions away from the aperture 140. In thisway, the plasma and the ions remain within the plasma chamber 105.Again, ions and excited or metastable neutrals from the plasma may bedeposited on the plasma chamber walls 107 of the plasma chamber 105, aswell as the dielectric window 125.

In either embodiment, the generation of this plasma produces ions andexcited neutrals, some of which attach to the inner surfaces of theplasma chamber walls 107, creating a coating on those surfaces. Thisconditioning process may be performed for between 30 minutes and 6hours. This process may be repeated periodically, such as every 24hours, although the amount of time is not limited by this disclosure. Inother embodiments, this conditioning process may be performed until acoating of a certain thickness has been created.

The use of multiple source gasses allows variations in both theconditioning process and the ion implantation process. For example, bycombining the feedgas with the conditioning gas in the ion implantationprocess, the deleterious effects of the fluorine ions may be reduced.For example, without being limited to any particular theory, theintroduction of hydrogen, in the form of hydrogen molecules or hydrides,may create a film or coating on the dielectric window 125. This mayserve to protect the dielectric window 125, which reduces the amount ofcontaminants originating from the dielectric window 125 that arecontained in the extracted ion beam 180. In addition, the conditioninggas may coat the inner surfaces of the plasma chamber walls 107, whichmay be another source of contaminants. This coating may reduce theinteraction between fluorine ions and the inner surfaces of the plasmachamber walls 107, reducing the amount of contaminants generated.

The introduction of a conditioning gas may reduce the creation ofcontaminants and the incorporation of these contaminants in the ionbeam.

In one embodiment, the ion implantation process is performed using acombination of the feedgas in the feedgas container 170 and theconditioning gas in the conditioning gas container 175. In anotherembodiment, the ion implantation process is performed using acombination of the feedgas and the co-gas disposed in the third gascontainer 176. As described above, the addition of other ions, such ashydrogen, germanium, phosphorus or silicon, may reduce the deleteriouseffect of halogens on the plasma chamber walls 107 and the dielectricwindow 125.

In a third embodiment, the ion implantation process is performed using acombination of the feedgas, the conditioning gas and the co-gas. Theamount of each gas can be tuned to achieve the desired beam currentwhile remaining below a predetermined contaminant level.

As stated above, the addition of at least a second source gas (which maybe the conditioning gas, the co-gas or both) may reduce the amount ofcontaminants introduced into the ion beam.

Thus, an extracted ion beam 180 having reduced beam impurity can becreated by using at least two source gasses. The first source gas, orfeedgas, may be a species than contains both boron and fluorine, such asBF₃ or B₂F₄. The second source gas may be the conditioning gas, which iscomprised of hydrogen gas, a borane, and a filler gas, where the fillergas is a hydride of a Group 4 or Group 5 element. Alternatively, thesecond gas may be the co-gas, which is a hydride of a Group 4 or Group 5element. In some embodiments, the second source gas may comprise boththe conditioning gas and the co-gas.

These two source gasses are introduced into a plasma chamber 105 of anion source 100, either simultaneously or sequentially, where they areionized. The ion source may use RF energy generated by RF antenna 120.In another embodiment, the ion source may utilize the thermionicemission of electrons using an IHC. Other methods of ionizing a gas mayalso be used by the ion source. These two source gasses may beintroduced such that between 60-95% of the total gas (by volume) isfeedgas, while the remainder is the second source gas with the amount of5-40% of the total gas (by volume). Ions from both source gasses areextracted through aperture 140 through use of electrodes 130, 150 andaccelerated toward a workpiece 160, where they are implanted into theworkpiece 160. As described earlier, these ions are not mass analyzed,meaning that all extracted ions are implanted into the workpiece 160.

As described above, the ion source 100 may also operate in aconditioning mode. For example, the inner surfaces of the plasma chamberwalls 107 of the ion source 100 may be conditioned prior to the implantprocess. The conditioning gas is introduced into the plasma chamberduring the conditioning mode.

In some embodiments, the conditioning gas comprises a hydride containingthe desired dopant species, which is used to condition the plasmachamber walls 107 and the dielectric window 125. The desired dopantspecies may be the dopant that is to be used during the subsequent ionimplantation process. In other words, in scenarios where the feedgasincludes boron, which is to be implanted into the workpieces during theion implantation process, a borane may be used as the conditioning gasduring the conditioning process. This borane may be diborane (B₂H₆),pentaborane (B₅H₉), decaborane (B₁₀H₁₄), or any other borane. If adifferent dopant is to be implanted, a different hydride may be used asthe conditioning gas.

As described above, diborane is unstable (at room temperature or generaloperating temperatures) and is therefore traditionally stored withhydrogen gas, typically in ratios of 30% or less (diborane to totalvolume). In this embodiment, the conditioning gas may be a mixture ofdiborane and hydrogen gas. In another embodiment, the conditioning gascontainer 175 is filled with a mixture of gasses, which includes up to30% diborane, 10-30% filler gas, and the remainder being hydrogen gas.In some embodiments, less than 50% of the conditioning gas is made up ofhydrogen gas. As described above, the filler gas is a hydride of a Group4 or Group 5 element, which contributes to the stability of diborane inthe absence of pure hydrogen gas.

In some embodiments, the co-gas is also introduced during theconditioning process. The co-gas may facilitate better ignition of theplasma, as compared to using only the conditioning gas. The use of aco-gas yields multiple benefits, such as better ignition of the plasmaat lower gas amounts than diborane-only, and a stronger protective filmon the plasma chamber walls. This enables the ion implantation processto be performed for longer periods of time, which improves productivity.

The amount of co-gas may be varied. For example, in some embodiments,the co-gas may be between 10-40% of the total gas introduced into theplasma chamber 105 during the conditioning process. In otherembodiments, the co-gas may be between 20-40% of the total gas. In yetother embodiments, the co-gas may be about 30% of the total gasintroduced during the conditioning process.

FIG. 2 shows the ion mass spectrum observed during a conditioningprocess using a mixture of conditioning gas and co-gas. In this figure,the conditioning gas is a mixture of 30% diborane and 70% hydrogen gas,and the co-gas is phosphine. The volume of conditioning gas is 65% ofthe total gas introduced. Note that the most abundant ion species arehydrogen (H_(x) ⁺), while the boron species is barely detectable.Hydrogen is known to etch the inner surfaces of the plasma chamber walls107 and the dielectric window 125. A reduction in the number of hydrogenions may be beneficial in reducing the contaminants present in the ionbeam generated during the subsequent ion implantation process.Therefore, a conditioning gas that replaces some of the hydrogen gas inthe conditioning gas container 175 with a filler gas, which comprises ahydride of a Group 4 or Group 5 element, may help reduce the etching ofthe plasma chamber walls 107.

In one specific example, BF₃ or B₂F₄ is used as the feedgas to implantthe workpiece. In other words, BF₃ or B₂F₄ is disposed in feedgascontainer 170. Prior to the ion implantation process, the plasma chamberwalls 107 of the ion source 100 are conditioned. Conditioning isperformed by introducing gas from the conditioning gas container 175 tothe plasma chamber 105. The conditioning gas container 175 is used tostore the conditioning gas. As described above, the conditioning gas maybe a combination of diborane and hydrogen gas, where roughly 30% of thetotal gas is diborane. In another embodiment, the conditioning gasdisposed in the conditioning gas container 175 may be a mixture ofdiborane (up to 30%), a filler gas (10-30%) and hydrogen gas. In someembodiments, less than 60% of the conditioning gas is made up ofhydrogen gas. In other embodiments, less than 50% of the conditioninggas is made up of hydrogen gas. As stated above, the filler gas is ahydride of a Group 4 or Group 5 element.

In some embodiments, gas from the third gas container 176 is alsointroduced during the conditioning process. As described above, thethird gas container 176 is used to store the co-gas. This co-gas may be,for example, a noble gas, such as helium, argon, krypton or xenon; aGroup 4 hydride, such as SiH₄, Si₂H₆ or GeH₄; or a Group 5 hydride, suchas PH₃ or AsH₃. Of course, this list is not exhaustive and othermolecules may be used as the co-gas during the conditioning process.

A plasma is generated using the conditioning gas and optionally theco-gas. In some embodiments, the voltages of the electrodes 130, 150 aresuch that ions are not extracted through the aperture 140. However, inother embodiments, ions from the plasma may be extracted during theconditioning process. This conditioning process serves to coat theplasma chamber walls 107 and dielectric window 125 so that impuritiesand other contaminants found in the plasma chamber walls 107 and thedielectric window 125 are isolated from the plasma. This coatingcontains the dopant found in the conditioning gas, which may be a Group3 element, such as boron. The coating may also contain molecules foundin the filler gas and in the co-gas, such as Group 4 elements, such asgermanium or silicon; or Group 5 elements, such as phosphorus orarsenic. A sufficient thickness of coating may be applied. The durationof the condition procedure may be based on elapsed time, such as between30 min and 6 hours, or may be based on measured thickness of the coatingas it accumulates on the plasma chamber walls 107.

The conditioning process may be performed for between 30 min and 6hours, although other durations of times are also possible. After theconditioning process is completed, the ion implantation process maybegin.

During the ion implantation process, feedgas from the feedgas container170 is introduced into the plasma chamber 105. As described above, thisfeedgas may be a molecule that contains the dopant and fluoride, such asBF₃ or B₂F₄, although other gasses may also be used. It should be notedthat the dopant used in the ion implantation process may be the same asdescribed above regarding the conditioning process. Additionally, atleast one of the conditioning gas and co-gas may also be introduced tothe plasma chamber 105 from its respective gas container 175, 176.

The gasses are then energized into a plasma, and extracted by applying abias voltage to electrodes 130. The extracted ions are then directedtoward a workpiece 160, where they are implanted without first beingmass analyzed.

This ion implantation process is used for a plurality of workpieces 160and may continue for a specific time period, or may be terminated whenthe level of contaminants in the extracted ion beam reaches apredetermined level. For example, the ion implantation process maycontinue until the level of contaminants reaches about 1% of the totaldopant beam current, although other contamination levels may beselected.

In summary, the conditioning process utilizes gasses from theconditioning gas container 175 and optionally the third gas container176. The ion implantation process utilizes gasses from the feedgascontainer 170, and gas from at least one of the conditioning gascontainer 175 and the third gas container 176.

The inclusion of a filler gas in the conditioning gas container 175reduces the amount of hydrogen contained in the conditioning gas. Thismay reduce the amount of etching that occurs on the plasma chamber walls107. A reduction in etching may reduce the amount of contaminants in theextracted ion beam 180 that is used in the subsequent ion implantationprocess. Additionally, less etching may also reduce the frequency atwhich the conditioning process is performed.

The inclusion of the conditioning gas or the co-gas to the feedgasduring the ion implantation process may help reduce the contaminantsthat are extracted from the plasma chamber 105.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are intended to fall within the scope ofthe present disclosure. Furthermore, although the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize that its usefulness is not limited thereto andthat the present disclosure may be beneficially implemented in anynumber of environments for any number of purposes. Accordingly, theclaims set forth below should be construed in view of the full breadthand spirit of the present disclosure as described herein.

What is claimed is:
 1. An apparatus for processing workpieces,comprising: an ion source having a plasma chamber defined by adielectric window, a plurality of plasma chamber walls and an aperture;an RF antenna disposed outside the plasma chamber proximate thedielectric window; a feedgas gas container, containing fluorine and adesired dopant species, in communication with the plasma chamber; and aconditioning gas container, containing a conditioning gas, theconditioning gas comprising a hydride containing the desired dopantspecies and a filler gas, the filler gas comprising a hydride of a Group4 element or a hydride of a species having an opposite conductivity ofthe desired dopant species.
 2. The apparatus of claim 1, furthercomprising a coating disposed on the plasma chamber walls.
 3. Theapparatus of claim 2, wherein the coating is formed by ionizing theconditioning gas in the plasma chamber.
 4. The apparatus of claim 2,wherein the coating comprises the desired dopant species.
 5. Theapparatus of claim 4, wherein the coating further comprises the Group 4element or the species having an opposite conductivity of the desireddopant species.
 6. The apparatus of claim 1, wherein the desired dopantspecies comprises boron.
 7. The apparatus of claim 6, wherein the fillergas comprises a hydride of a Group 5 element.
 8. The apparatus of claim1, wherein the conditioning gas disposed in the conditioning gascontainer further comprises hydrogen gas.
 9. The apparatus of claim 8,wherein less than 50% of the conditioning gas disposed in theconditioning gas container comprises hydrogen gas.
 10. The apparatus ofclaim 1, further comprising a third gas container in communication withthe plasma chamber, containing a co-gas, wherein the co-gas comprises anoble gas, a hydride of a Group 4 element or a hydride of a specieshaving an opposite conductivity of the desired dopant species.
 11. Theapparatus of claim 1, further comprising an electrode disposed outsidethe aperture to extract and focus positively charged ions from withinthe plasma chamber through the aperture and toward a workpiece.
 12. Anapparatus for processing workpieces, comprising: an ion source having aplasma chamber defined by a dielectric window, a plurality of plasmachamber walls and an aperture; an RF antenna disposed outside the plasmachamber proximate the dielectric window; and a coating disposed on theplasma chamber walls, wherein the coating comprises a desired dopantspecies.
 13. The apparatus of claim 12, wherein the coating furthercomprises a Group 4 element or a species having an opposite conductivityof the desired dopant species.
 14. The apparatus of claim 12, whereinthe desired dopant species comprises boron.
 15. The apparatus of claim14, wherein the coating comprises boron and at least one of arsenic,phosphorus, silicon, and germanium.
 16. The apparatus of claim 12,further comprising an electrode disposed outside the aperture to extractand focus positively charged ions from within the plasma chamber throughthe aperture and toward a workpiece.
 17. The apparatus of claim 12,further comprising a feedgas gas container, containing fluorine and thedesired dopant species, in communication with the plasma chamber. 18.The apparatus of claim 12, further comprising a conditioning gascontainer, containing a conditioning gas, the conditioning gascomprising a hydride containing the desired dopant species and a fillergas, the filler gas comprising a hydride of a Group 4 element or ahydride of a species having an opposite conductivity of a desired dopantspecies.
 19. The apparatus of claim 18, wherein the desired dopantspecies is a Group 3 element and the filler gas comprises a hydride of aGroup 5 element.
 20. The apparatus of claim 18, wherein the conditioninggas disposed in the conditioning gas container further compriseshydrogen gas.
 21. The apparatus of claim 20, wherein less than 50% ofthe conditioning gas disposed in the conditioning gas containercomprises hydrogen gas.
 22. The apparatus of claim 18, furthercomprising a third gas container in communication with the plasmachamber, containing a co-gas, wherein the co-gas comprises a noble gas,a hydride of a Group 4 element or a hydride of a species having anopposite conductivity of the desired dopant species.